It has been known that heart patients may benefit from total artificial hearts. Such patients include those who die from pump failure following open heart surgery, patients who have intractable heart failure and patients who die from cardiogenic shock. A greater number could be saved by providing an auxiliary heart or pump in the cardiovascular system. It is heretofore been proposed that a left ventricular assist pump be provided in a line between the left ventricle and the aorta which functions to bypass some of the blood and thereby assist the heart.
The advantage of a left ventricular assist device is that it assists the human heart in maintaining its pump action, alters the physiology of the patient to a lesser degree and is less likely to interfere with other body functions. Theoretically, the device would require less energy allowing the energy source to be smaller.
Left ventricular assist devices which are provided between the left ventricle and the aorta function to draw blood from the left ventricle and bypass the blood through a pump to the aorta. Among the types that have been proposed are "A CamType Electric Motor-Driven Left Ventricular Assist Device", Rosenberg et al, Journal of Biomechanical Engineering, Vol. 104, 1982, p. 214-220; "Experimental Results for Chronic Left Ventricular Assist and Total Artificial Heart Developement", Y. Nose et al, ARTIFICIAL ORGANS, Vol. 7, No. 1, 1983, p. 55-63; "Design of Pusher-Plate-Type Left Ventricular Assist Device Based on Mechanical Analyses", K. Hayashi et al, ARTIFICIAL ORGANS, Vol. 8, No. 2, 1984, p. 204-214; "Investigations With an Implantable, Electrically Actuated Ventricular Assist Device", Bernard, et al J. Thorac Cardiovasc Surg 88; 11-21, 1984.
Among the objectives of the present invention are to provide an auxiliary artificial heart which is easier to attach because it is adapted to be connected to the aorta only; which is compact, durable, efficient, light weight, has a low inertia; which can be adjusted to provide or change volume and wherein the diaphragm may be readily renewed or replaced.
In accordance with the invention the auxiliary artificial heart comprises a pump having a single opening that is connected to the aorta and is operable in synchronism with the heart of the patient to assist the normal function of the heart. The auxiliary artificial heart comprises a housing having the single opening therein and a diaphragm which is movable toward and away from the opening by a rotating reversible electric stepping motor. Rotation of the motor rotates circumferentially spaced roller pins which extend radially inwardly into engagement with a helical groove of a screw attached to the diaphragm to translate the screw and move the diaphragm toward and away from the opening. The housing is sealed such that the differential pressure caused by movement of the screw assists the diaphragm in its movement.